Prior patents relevant to the instant invention include: (1) U.S. Pat. No. 4,640,461 (Williams) directed to a self educting foam fog nozzle; (2) U.S. Pat. No. 5,779,159 (Williams) directed to a peripheral channeling additive fluid nozzle; and (3) U.S. Pat. Nos. 5,275,243; 5,167,285 and 5,312,041 (Williams) directed to a chemical and fluid or duel fluid ejecting nozzle. Also relevant is the prior art of automatic nozzles, including (4) U.S. Pat. Nos. 5,312,048; 3,684,192 and 3,863,844 to McMilian/Task Force Tips and U.S. Pat. Nos. Re 29,717 and 3,893,624 to Thompson/Elkhart Brass. Also of note are U.S. Pat. No. 5,678,766 to Peck and PCT Publication WO 97/38757 to Baker.
Maintaining a constant discharge pressure from a nozzle tends to yield a constant range and “authority” for the discharge while allowing the nozzle flow rate to absorb variations in head pressure, as it were. In certain applications, such as vapor suppression, a fixed fire fighting nozzle is particularly useful if it self regulates to discharge at an approximately constant or targeted pressure. The discharge pressure tends to govern what is referred to as the “authority” of the discharge stream and to a certain extent the stream's range. A constant discharge pressure comes closer to a consistent delivery of a stream at a fixed range.
One specific application in which a self-regulating nozzle may be useful is in a fixed protection system that includes nozzles permanently stationed around locales subject to the leakage of toxic chemicals. Upon leakage, a permanently stationed configuration of constant pressure nozzles, possibly under remote control, could be activated to provide a predesigned curtain of water/fog to contain and suppress any toxic vapors. In such circumstances it may be optimal for nozzles to discharge their fluid with a (more or less) constant range and authority as opposed to having their discharge structured and regulated for a relatively constant flow rate, as is more typical for nozzles. Water/fog created with approximately constant range and authority, while operating under conditions of varying head pressure, will more reliably curtain a preselected region from a fixed locale.
Frequently nozzles are structured to deliver a pre-set gallons-per-minute flow rate, assuming a nominal head pressure, such as 100 psi at the nozzle. As the head pressure actually available to a nozzle in an emergency can vary, flow rate remains more consistent in such designs than range. Alternately structuring a nozzle to target and regulate discharge pressure lets flow rate vary with variations in delivered pressure while keeping range more constant.
The present invention discloses an improved pressure regulating nozzle designed to effectively discharge a fire extinguishing fluid at a pre-selected discharge pressure and range, up to a targeted flow rate, and thereafter to maintain relatively constant flow rate while discharge pressure and range are allowed to increase. A preselected discharge pressure, for example, would likely be approximately 100 psi, but the preselected pressure could vary, and might more optimally be selected to be approximately 120 psi. Likewise a targeted flow rate is selected. This selection of targeted flow rate need only be approximate. The inventive design combines the benefit value of maintaining range at low supply pressures while maintaining flow rate at higher supply pressures, thereby accommodating minimum range requirements on the one hand while more easily accommodating self-educting features for foam concentrates and a capacity to throw fluid chemicals such as dry powder on the other hand, where possible.
The invention includes enhanced eductive techniques, for both peripheral and central channeling, which enhanced eduction can be particularly helpful in automatic nozzles or when throwing chemicals such as dry powder.
A typical fire fighting nozzle may be designed to be adjusted to operate over a range of flows, such as 500 gallons-per-minute to 2000 gallons-per-minute, given a certain discharge pressure (typically assumed to be around 100 psi). In an automatic nozzle, to select and self regulate for pressure while allowing flow to vary, nozzle design incorporates a self-adjusting baffle or the like proximate the nozzle discharge. In general, when fluid pressure at such a baffle, sensed directly or indirectly, is deemed to lie below a selected pressure, the baffle is structured in combination with the nozzle body to “squeeze down” on the effective size of the discharge orifice. When pressure builds up at the baffle, sensed directly or indirectly, to reach or exceed a preselected pressure, the baffle is structured to cease squeezing down and, if necessary, to shift to enlarge the effective size of the nozzle discharge orifice. Enlargement continues, in general, until the discharge pressure reduces to the selected value. Adjustments in the size of the discharge port cause flow rate to vary but the discharge tends to have constant “authority” and range.
The instant invention achieves a hybrid pressure regulating and flow regulating system. Designs for flow and embodiments of automatic nozzles are themselves discussed in detail in the above applications incorporated herein by reference. This invention includes further improvements in self-adjusting nozzles. To review the basics of a nozzle, a fire fighting nozzle defines a conduit for a fire fighting fluid that terminates in a discharge orifice. The fire fighting fluid is usually water, and while it may be treated and discussed as water herein, it should be understood that nozzle technology is applicable to various fire fighting fluids. The conduit and discharge orifice structure are typically designed in combination to recover, to the extent practical, fire fighting fluid pressure available from the fluid source. Recovery of pressure affects range.
Given generally anticipatable supply ranges, in pressure and flow, for the fire fighting fluid (industry standard sources of pressurized water might be anticipated to vary between 75 psi and 150 psi,) nozzle body conduits and discharge orifices may be designed to define an effective, or practical, flow window. For instance, a “two and one-half inch” nozzle might be adjustable to effectively flow between 150 GPM and 600 GPM while a “sixteen inch” nozzle might be adjustable to effectively flow between 4,000 GPM and 16,000 GPM, both being affected by variations in supply pressure or quantity.
An adjustable discharge orifice, automatic or manual, is designed to be adjusted within a range of flow effectiveness of a nozzle body. Fluid flow rate through the nozzle may vary within a nozzle's effective flow window, again taking into account variations in source supply and pressure. Minimum limits on an effective flow window include a minimum effective “gap” size, or a minimum effective width of a typically annular discharge orifice. Below a certain “gap” size the thickness of the wall of water discharged diminishes such that the water wall tends to disintegrate and nozzle throw performance suffers. On the other end, a “gap” can get so large that the fixed conduit bore structure itself governs throw. There is thus a practical limit to the flow of water that can be efficiently flowed through a nozzle bore.
It is to be understood that although adjustable discharge orifices may be traditionally designed in terms of an adjustable baffle within a conduit, any element of a nozzle structure defining at lest in part the discharge orifice, including an outer wall portion, in theory could be an adjustable element. We refer to traditional designs for convenience, in regard to an adjustable baffle located in a conduit where the adjustment of the baffle forward and backward governs gap size. There is a range in which such adjustment is effective. The range is related to an effective or practical fluid flow window of the nozzle.
A given conduit and discharge orifice contribute to defining a “k” factor for a nozzle. Flow rate and discharge pressure are related by the formula: r=k√{square root over ( )}p, where r is the flow rate, p the discharge pressure and k the “k” factor. It can be seen that for a constant k, flow varies with the square root of pressure. With a fixed conduit and discharge orifice, discharge pressure p rises with increased supply pressure from the fluid source while flow rate “tends” to remain relatively constant, at least as compared to pressure, because it only increases with the square root of pressure.
“Automatic” nozzles have automatically adjustable discharge orifices. Automatically adjustable discharge orifices are typically designed to maintain a selected discharge pressure, such as 100 psi. In such automatic nozzles, there is typically a means for sensing discharge fluid pressure and a biasing means structured to adjust the discharge orifice (sometimes referred to as the “gap”) until the sensed discharge pressure is approximately the preselected discharge pressure. (The word “approximately” is used herein throughout because automatic nozzle designs are only “approximately” accurate.) As a result of sensing and adjustment, a discharge orifice or gap is narrowed or widened so that the sensed discharge pressure is approximately the selected discharge pressure. When the discharge orifice or gap is narrowed, fluid flow rate through the nozzle is reduced. As the gap is widened, fluid flow rate through the nozzle is increased. As discussed above, however, if the discharge orifice of the nozzle were to remain fixed, the “k” of the nozzle would remain fixed and flow rate would “tend” to remain fixed while discharge pressure would vary with supply pressure. (Flow rate varies only with the square root of pressure.).
If a foam concentrate is to be metered into a fluid stream at a constant percent (eg 3%, or 6%), a relatively constant flow rate of the fluid stream is an advantage, as it allows a metering device on the foam concentrate to be set. Further, a relatively constant flow rate with a high discharge pressure may be desired in some circumstances. E.g. high pressure helps some concentrate to create a better foam. In a nozzle that discharges a chemical, such as a dry powder, within a fire fighting fluid, it may be desirable to limit fluid flow rate to avoid unnecessary wetting of the powder. Further, nozzles that adjust without limitation to produce a selected discharge pressure can waste water if there is a limited supply of water.
Thus, a relatively constant flow rate from a nozzle can be an advantage in several situations, but if the supply pressure is weak, or if a nozzle is set at a fixed distance from a fire, a relatively constant pressure may be an advantage. (Constant pressure tends to maintain range for the nozzle even though flow rate may vary). Within the duration of one fire, the relative importance of constant pressure and of constant flow rate can shift.
The hybrid, selectively automatic nozzle of the instant invention provides the best of two worlds. The adjustable stop (or any other such adjustable means) can be set so that an automatically adjustable discharge orifice is provided, as in an automatic nozzle, for flow rates up to a given point (in a nozzle's effective flow window). If supply pressure goes low, range can be maintained. However, if a targeted fluid flow rate within the nozzle is reached, a stop or the like causes the discharge orifice to cease adjusting. Now discharge pressure rises with supply pressure but fluid flow rate tends to remain approximately constant (again, rising only in proportion to the square root of the pressure). Metering foam concentrate in a preselected proportion is thus more reliable, with fixed flow rate.